Slurry tolerant pilot operated relief valve

ABSTRACT

Cartridge-style fluid control devices are provided that are static pressure independent and capable of repeatable, reliable, particulate insensitive performance in service conditions typical of downhole intervention environments.

This application is the National Stage of International Application No.PCT/US04/029831, filed 14 Sep. 2004, which claims the benefit of U.S.Provisional Patent Application No. 60/503,042, filed 15 Sep. 2003.

FIELD OF THE INVENTION

This invention pertains to fluid control devices for metering,maintaining, and isolating fluid pressure and flow between two or moresources.

BACKGROUND OF THE INVENTION

Fluid control is routinely practiced within a wide variety ofindustries. Control is typically achieved using devices that arespecifically designed to perform a unique control operation. Examples ofsuch control devices are pressure relief valves, pressure regulators,back-pressure regulators, velocity fuses, mass flow controllers, pilotoperated valves, check valves, and shuttle valves.

Pressure is typically communicated from one source to another via theflow of gas or liquid. Operational challenges arise when the flow usedto communicate pressure is laden with particulates. These particulatesintroduce the potential for a device to lose functionality as a resultof solids becoming lodged in a device's moving parts, as well as damageresulting from the cutting capacity of high velocity, particle-ladenfluid streams passing over a device's sealing components. The use ofrigid seal materials such as metal or thermoplastics enhance thedurability of a device, but compromise the sealability of the device.

For example, a steel ball could never seal a circular steel aperture ifa sand grain was wedged between the steel ball and the edge of theaperture (or if the edge of the aperture was slightly nicked). If theball was made of a pliable material such as rubber, the ball could sealthe circular aperture because the sand grain could imbed in the ball andthe ball could then fully contact the perimeter of aperture. While therubber ball is a superior sealing material, it is also highlysusceptible to damage from the cutting action of high velocity fluidstreams.

Many valving designs directly, or indirectly, involve three pressures:1.) inline high pressure source; 2.) inline low pressure source; and 3.)a static pressure source, e.g., ambient pressure in a spring cavity.Valve designs that involve an isolated, or sealed, static pressureexhibit limited functionality in a downhole environment. The primaryreason is that most downhole operations are performed in a well that isfilled with liquid, thus the static pressure increases as a function ofdepth. This change in static pressure results in a change in valveperformance as a function of depth. Valve designs that provide freestatic pressure communication to all actuating parts within the systemenable depth (or static pressure) independence. This is because fluidbased valve actuation forces result from differential pressures actingupon an area. Since the actuation forces are based on the differencebetween pressure sources, the reference pressure (or static pressure)that is common to all sources is canceled out, and the performance ofthe valve becomes depth independent.

An additional criteria required of downhole fluid control operations isrelated to size. Wellbores of various diameters are created in an effortto optimize the economic impact of a field development; and valves mustbe smaller than the wellbore diameter in which they are deployed. As aresult, valves with small external dimensions possess a larger portfolioof accessible intervention wells than larger valves of similar function.In addition, when valves are deployed downhole they are not readilyaccessible for servicing; thus significant expense is typically incurredif valve failures occur during an intervention program. This emphasizesthe need for downhole valves to be highly reliable.

For various applications, certain advantages can be realized bydesigning a control valve device in the form of a cartridge valve. Acartridge style control valve offers the following benefits: 1.) theability to interchangeably deploy the same valve in multiple tools thatrequire the given valve's control function; 2.) the ability toincorporate the valve into cartridge valve based logic systems; 3.) theability to verify functionality before deployment by performingbench-top surface testing of the valve; 4.) simplified valve replacementand servicing; and 5.) cartridge valves are well suited for deploymentin parallel, or series (e.g., for the purpose of redundancy in safetycritical applications).

Most downhole fluid control devices are deployed as a single unit orconnected in series with other downhole components. The systems aregenerally comprised of a combination of annular based components,springs, and/or balls. Annular based components are defined as partsthat are symmetric about the centerline of the valve. The valves tend tohave rigid seal materials and are designed in a fashion that aresusceptible to compromised functionality due to particulate bridgingbetween the rigid seal materials. Current technology does not provide asuitable physical design, or design concept for the problem.

A need exists for small cartridge-style fluid control devices that arestatic pressure independent and capable of repeatable, reliable,particulate insensitive performance in service conditions typical ofdownhole intervention environments. An object of this invention is toprovide such fluid control devices. Other objects will become apparentthrough consideration of the following specification together with theaccompanying drawings.

SUMMARY OF THE INVENTION

In one embodiment, the present invention is a pressure-actuated valvecomprising: (a) a valve body with a cavity formed therein, said cavitybeing defined by a retaining cap at one end of the valve body andextending from there for a length until an annular wall is encountered,said annular wall separating the cavity for the remainder thereof into acentral bore and an outer annular region, said valve body having twopassages from outside the valve body into the bore servinginterchangeably for inlet and outlet of fluids (possibly containingsmall solids) whose flow is to be controlled by the valve, and anannular valve seat disposed in said bore between said inlet and saidoutlet, said inlet and outlet being disposed in the bore remote from theretaining cap, said retaining cap having a passage through it providingcommunication between outside the valve body and the valve body cavity;(b) a plunger with a head and a sealing end, said plunger being movablydisposed within said bore with said head end extending out of the boreinto the valve body cavity, said head being larger than the outerdiameter of said annular wall enclosing said bore, said sealing endbeing adapted for operative engagement with said valve seat thuspreventing fluid flow between the inlet and the outlet and constitutingthe off position for the valve, said plunger having a range of travel inthe bore to a valve-open position at which the plunger head contacts theretaining cap, said plunger's length being determined such that fluidpassage between the inlet and the outlet is substantially unobstructedby the plunger in the valve-open position; (c) a spring disposed in saidouter annular region surrounding said bore such that the plunger headcontacts the spring requiring compression of the spring in order for theplunger's sealing end to contact the valve seat wherein, in operation, ahigh-pressure actuating fluid entering the valve body cavity through thepassage in the retaining cap exerts pressure on the plunger head tendingto force the plunger toward the valve seat and closing the valve whenthe fluid pressure overcomes the spring's resistance; and (d) a sealbetween the plunger and the bore disposed between (i) the fluid inletand outlet and (ii) the end of the bore nearer to the retaining cap,said seal isolating the high-pressure actuating fluid from the fluidflowing between said valve body inlet and outlet.

In some embodiments of the present invention, the valve furthercomprises a bushing movably disposed between the spring and the plungerhead, with inner diameter large enough to fit movably around the annularwall defining the central bore. The bushing can serve as a shimadjustment for the valve's operation, thereby determining the thicknessof the bushing. In some embodiments of the invention, the valve body isformed for cartridge-style deployment. In some embodiments of theinvention, the spring is installed under compression, i.e., it is in astate of partial compression even when the plunger head is fully upagainst the retaining cap.

DESCRIPTION OF THE DRAWINGS

The advantages of the present invention will be better understood byreferring to the following detailed description and the attacheddrawings in which:

FIG. 1A illustrates a valve according to this invention in the openposition; and

FIG. 1B illustrates a valve according to this invention in the closedposition.

While the invention will be described in connection with its preferredembodiments, it will be understood that the invention is not limitedthereto. To the extent that the following description is specific to aparticular embodiment or a particular use of the invention, this isintended to be illustrative only, and is not to be construed as limitingthe scope of the invention. On the contrary, the invention is intendedto cover all alternatives, modifications, and equivalents which may beincluded within the spirit and scope of the present disclosure, asdefined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

The following discussion describes the invention within the context ofoilfield downhole intervention technology, although the invention is notlimited to such use.

An application in which a valve according to this invention isparticularly useful is fracture stimulation, especially when used with acoiled tubing deployed intervention tool that comprises an inflatablepacker, slips, and a circuit of cartridge valves that perform tasks as afunction of applied pressure. In wellbores with multiple zones open(multiple sets of reservoir intervals in communication with the wellboreat different depths), the possibility exists that flow will exit onereservoir interval and travel through the wellbore into anotherreservoir interval. This phenomenon is called cross-flow and it isdriven by a pressure imbalance between reservoirs. If a bottom holeassembly (i.e., BHA or intervention tool) is located between two zonesthat are cross-flowing, the potential exists for the BHA to be pusheduphole and buckle the coiled tubing, pulled downhole and pull apart theBHA or coiled tubing, or damage the BHA as debris passes by the tool athigh rates.

This phenomenon can be particularly significant while an inflatablepacker is being inflated and deflated. This is because during theinflation and deflation process the packer reaches a point where thepacker has effectively shut-off the cross-flow fluid passing between thecasing and the packer but has not yet contacted the casing with enoughforce to anchor it in place. At this time, the differential pressurethat exists between the cross-flowing reservoir intervals is applied tothe full cross-sectional area of the un-anchored BHA. Depending on thespecific application, the resulting forces could be significant andpromote the aforementioned results. In an effort to avoid the potentialresults of operating an inflatable packer in the presence of cross-flow,the pressure across the packer is preferably equalized through thecenter of the packer until it is firmly anchored to the wall.

To achieve this goal, a pilot operated relief valve according to thisinvention is incorporated into the BHA design. The valve equalizeswellbore pressure across the inflatable packer while it is inflating andthen closes the equalization path after the packer has fully contactedthe casing walls. During packer deflation the valve opens prior torelease of the packer from the casing wall and remains open during thedeflation process. The valve is designed to be pressure actuated using apilot pressure from the coiled tubing. The use of coiled tubing pressureto control the valve's operation enables the valve to actuate at theproper time relative to the packer inflation and deflation cycle.

An application in which the intervention tool is particularly useful isreservoir fracture stimulation using sand or proppant. Thus, the fluidenvironment in which the valve is expected to operate reliably is one inwhich sand and proppant may pass through the valve under normaloperating conditions or under upset operating conditions. Since wellborefluids are typically laden with various particles, the valve design mustbe robust with respect to actuation and sealing in the presence ofparticulate debris.

The general function of a Pilot Operated Relief Valve (PORV) accordingto this invention is described below. The valve is designed to remainfully open when the actuating pressure remains below a pre-set value.When the actuating pressure surpasses this pre-set pressure, the closingprocess is initiated. When the valve is closed, the fluid pressureacting on the valve plunger does not have an effective area to act upon,thus the valve's function is independent of this pressure. This featureis particularly important if the intervention application involvesapplying significant pressure to the fluid in this passage (e.g.,fracture stimulation operations). Operation of the valve is described inconnection with a packer, as described above. The packer is not shown inthe drawings.

Referring to the drawings, the primary moving parts of a valve 10according to this invention are: (i) spring assembly 12 that preferablycomprises a plurality of springs or discs 12 a; (ii) a plunger 14 havinga head 14 a and a sealing end 14 b; and (iii) bushing 16. A valve 10according to this invention also comprises valve body 17 having a hollowspring support portion 17 a and a connector portion 17 b, valve bodysleeve 19, seat 26, seat housing 27, and retaining cap 18. A fluidpressure force acts at cross-sectional area 11 to move plunger 14 towardseat 26; i.e., high pressure fluid 13 above cross-sectional area 11 actson cross-sectional area 11 to push plunger 14 in the direction of seat26. Plunger 14 moves axially and its motion is governed by a forcebalance between the force of springs 12 pushing plunger 14 away fromseat 26 and the fluid pressure force acting at cross-sectional area 11pushing plunger 14 toward seat 26.

When valve 10 is in the open position, the force of springs 12 isgreater than the pressure force at cross-sectional area 11 and it pushesplunger 14 away from seat 26 and holds it against retaining cap 18. Flowis free to communicate in either direction between passage 20, for fluidfrom uphole of the packer, and passage 22, for fluid from downhole ofthe packer. High pressure actuating fluid 13 is isolated from fluid 23flowing between passages 20 and 22 by seals 15 in plunger 14 atcross-sectional area 11 and seals 28 on valve body 17.

As the pressure of actuating fluid 13 is increased above the pre-setclose value of valve 10, the pressure force at cross-sectional area 11overcomes the force of springs 12 (plus any breakaway friction forcefrom seals or O-rings 15 in plunger 14 at cross-sectional area 11) andbegins to push plunger 14 toward seat 26. As plunger 14 moves towardseat 26, flow begins to be restricted through the region between thebottom of plunger 14 and location 21. As bottom edge 24 of plunger 14reaches location 21, flow is significantly reduced. This reduction inflow, in combination with the vertical and inclined passage geometryleading up to location 21, allows particles to tumble away from location21 before plunger 14 enters the orifice of passage 22. This reduction inflow rate results in a reduction in particle delivery rate and particledelivery size to the pinch point at location 21, thus the likelihood ofparticles becoming lodged between plunger 14 and location 21 isdiminished. In addition, the curved geometry of the sharp location 21edge insures that only a small number of particles could reside at thepinch point. The large plunger force attainable via the actuating fluidpressure acting on cross-sectional area 11 provides sufficient force toshear through a small number of particulate grains.

Referring now to FIG. 1B, as plunger 14 continues its downward stoke itenters the orifice of passage 22. The diameter tolerance between plunger14 and the orifice is preferably small in an effort to significantlyreduce the flow rate through valve 10 (e.g., about 0.13 mm to 0.25 mm,(0.005 in to 0.010 in)). If the flow direction is from passage 22 topassage 20, the significantly reduced flow rate limits the size ofparticles that can be carried against gravity to seat 26 of passage 22.If the flow direction is from passage 20 to passage 22, then the gapbetween plunger 14 and the orifice of passage 22 acts as a screen thatfilters all particles greater than the gap width. As a result,regardless of the flow direction between passages 20 and 22, there is aphysical mechanism that acts to minimize the size and delivery rate ofparticles to seat 26. Seat 26 is preferably designed with a 45° chamferto allow particles to fall from seat 26 under the influence of gravity,or to be squeezed off during the seating process.

In addition, seat 26 is preferably designed with a relatively smalldiameter decrease from the diameter of passage 22. The size of the smalllip that comprises the plunger contact portion of seat 26 (e.g., about0.25 mm (0.010 in)) provides an upper bound on the particle diameterthat could fit on the lip, assuming that it was possible for theparticle to maintain a stable position on the 45° chamfer. In addition,the low-profile nature of seat 26 provides minimal restriction to flowwhen valve 10 is fully open.

Valve 10 is re-opened by reducing the actuating pressure and allowingthe spring force to push plunger 14 back to retaining cap 18. Thepressure at which valve 10 becomes fully open is nominally similar tothe pre-set pressure that initiated the valve closing process. Aftervalve 10 is opened, fluid is able to freely exchange between passages 20and 22.

EXAMPLES

The following discussion provides a paper example that is based ondeployment of a pilot operated relief valve (PORV) according to thisinvention in a fracture stimulation application. For this example acoiled tubing deployed bottom-hole-assembly (BHA) is assumed and thisBHA is comprised of an inflatable packer and a circuit of cartridgevalves that perform tasks as a function of applied pressure. It is alsoassumed that packer inflation occurs via applied coiled tubing pressure,and the PORV port for actuation fluid (fluid 13 in the drawings) is incommunication with the coiled tubing. Additionally, it is assumed thatan independent flow passage exists through the center of the packer withone passage in the PORV (passage 20 in the drawings) in communicationwith the annular fluid uphole of the packer and another passage (passage22 in the drawings) being in communication with the fluid downhole ofthe packer. It is also assumed that the fracture stimulation is pumpedbetween the casing and the coiled tubing into an interval uphole of theinflated packer. It is also assumed that the fracture stimulationprocess occurs in a wellbore with several pre-existing reservoirintervals in communication with the wellbore below the location of theBHA.

It is assumed that the PORV is configured to remain open up to anactuating pressure of 13.8 MPa (2000 psi) and with a close pressure of34.5 MPa (5000 psi). With the BHA positioned between reservoir intervalsthat are in communication with the wellbore, the possibility exists thatthe two intervals are in cross-flow communication. The application ofpressure to the coiled tubing initiates the packer inflation process. Asthe inflatable packer increases in diameter and begins to touch thecasing wall, the fraction of the cross-flow that was originally passingbetween the outside diameter of the packer and the inside diameter ofthe casing diverts into the equalization passage running through thecenter of the packer. Increasing the coiled tubing pressure toapproximately 13.8 MPa (2000 psi) anchors the packer to casing walls andinitiates the closing process for the pilot operated relief valve. Asthe coiled tubing pressure is increased the PORV begins to close, thepacker anchoring pressure increases, and the cross-flow induceddifferential pressure begins to build across the packer. Increasing thecoiled tubing pressure to 34.5 MPa (5000 psi) closes the PORV and places34.5 MPa (5000 psi) of anchoring pressure into the packer.

The stimulation program is initiated after the packer is firmly anchoredto the casing wall. Since the packer is sealed against the casing wallsand the PORV is closed, all stimulation fluids pumped down the annulusbetween the casing and coiled tubing are injected into the desiredreservoir interval. Since passage 20 (see the drawings) of the PORV isin direct communication with the fluid above the packer, the stimulationpressures applied to the annulus are directly applied to the plunger inthe PORV via passage 20. However, since the PORV is designed such thatthere is essentially no effective area for this stimulation pressure toact, the valve remains closed.

Following the stimulation, the coiled tubing pressure is decreased. Whenthe coiled tubing pressure and packer pressure reach approximately 13.8MPa (2000 psi) the PORV has completely re-opened and pressureequalization is fully enabled. Decreasing the coiled tubing pressure tozero allows the packer to release from the casing walls and deflate. Thestimulation is then complete and the BHA is free to move uphole.

Although this invention is well suited for use in oilfield downholeintervention technology, it is not limited thereto; rather, thisinvention is suitable for any application where fluid control isrequired. Additionally, while the present invention has been describedin terms of one or more preferred embodiments, it is to be understoodthat other modifications may be made without departing from the scope ofthe invention, which is set forth in the claims below.

1. A pressure-actuated valve comprising: (a) a valve body with a cavityformed therein, said cavity being defined by a retaining cap at one endof the valve body and extending from there for a length until an annularwall is encountered, said annular wall separating the cavity for theremainder thereof into a central bore and an outer annular region, saidvalve body having two passages from outside the valve body into the boreserving interchangeably for inlet and outlet of fluids (possiblycontaining small solids) whose flow is to be controlled by the valve,and an annular valve seat disposed in said bore between said inlet andsaid outlet, said inlet and outlet being disposed in the bore remotefrom the retaining cap, said retaining cap having a passage through itproviding communication between outside the valve body and the valvebody cavity; (b) a plunger with a head and a sealing end, said plungerbeing movably disposed within said bore with said head end extending outof the bore into the valve body cavity, said head being larger than theouter diameter of said annular wall enclosing said bore, said sealingend being adapted for operative engagement with said valve seat thuspreventing fluid flow between the inlet and the outlet and constitutingthe off position for the valve, said plunger having a range of travel inthe bore to a valve-open position at which the plunger head contacts theretaining cap, said plunger's length being determined such that fluidpassage between the inlet and the outlet is substantially unobstructedby the plunger in the valve-open position; (c) a spring disposed in saidouter annular region surrounding said bore such that the plunger headcontacts the spring requiring compression of the spring in order for theplunger's sealing end to contact the valve seat wherein, in operation, ahigh-pressure actuating fluid entering the valve body cavity through thepassage in the retaining cap exerts pressure on the plunger head tendingto force the plunger toward the valve seat and closing the valve whenthe fluid pressure overcomes the spring's resistance; and (d) a sealbetween the plunger and the bore disposed between (i) the fluid inletand outlet and (ii) the end of the bore nearer to the retaining cap,said seal isolating the high-pressure actuating fluid from the fluidflowing between said valve body inlet and outlet; wherein one of saidtwo passages into the bore for valve-controlled fluids is disposed suchthat it enters the bore non-axially into the side of the bore at alocation between the valve seat and the plunger head, thereby enablingno more than negligible fluid pressure on the plunger in a directiontending to force the valve open from a closed position; and wherein thenon-axial passage has a vertical and inclined passage geometry leadingup to an intersection where the non-axial passage intersects the bore,wherein the vertical and inclined passage geometry is adapted to resistparticle accumulation in the non-axial passage, and wherein theintersection between the non-axial passage and the bore is configured toresist particle settling at the intersection.
 2. The valve of claim 1,further comprising a bushing movably disposed between said spring andsaid plunger head, said bushing serving as a shim adjustment to thevalve operation, thereby determining the bushing's thickness.
 3. Thevalve of claim 1, wherein the other passage into the bore forvalve-controlled fluids is a continuation of said bore through the valvebody at the end of the valve body remote from the retaining cap.
 4. Thevalve of claim 1 wherein the clearance tolerance between the plunger andthe bore is between 0.13 mm and 0.25 mm.
 5. The valve of claim 1 wherethe valve seat is designed with a chamfer of approximately 45 degrees.6. The valve of claim 1, wherein said annular valve seat has a radialdimension of approximately 0.25 mm.
 7. The valve of claim 1, whereinsaid valve body is formed for cartridge-style deployment.
 8. The valveof claim 1, wherein said spring is designed to be in a state of partialcompression with said plunger head in contact with said retaining cap.9. The valve of claim 1, wherein said spring comprises a plurality ofstacked Belleville (disc) springs.